While the polar bear is an Ice Age species, genetic and fossil evidence suggests it barely survived the profound sea ice changes associated with the Last Glacial Maximum, one of the most severe glacial periods of the Pleistocene.

A map of sea ice extent at the climax of the Last Glacial Maximum (both perennial and seasonal ice), prepared with the help of a colleague, makes it possible to discuss what genetic and fossil evidence can tell us about the probable effects of glacial conditions on polar bears and ringed seals.

Posted onNovember 9, 2014|Comments Off on Polar bear listed as a migratory species by UNEP to restrict oil exploration & extraction

In a press release this afternoon, the Convention on the Conservation of Migratory Species of Wild Animals (CMS) announced it had added polar bears to their list of Appendix II migratory species. [CMS is a pseudo-arm of the UN Environment Programme, the UNEP1]

“The Polar Bear, the largest apex predator on Earth is affected by climate change that has led to the loss of 2 million m2 of sea ice. The Appendix II listing introduces the global perspective of existing threats to Arctic species stemming from shipping and oil exploration, making it a case for all CMS Parties.“

In its end of February report, the US National Snow and Ice Data Center (NSIDC) noted that Barents Sea ice was below average for this time of year (see Fig. 1 above, and Fig. 5 below) but suggested this was primarily due to natural variation driven by the Atlantic Multidecadal Oscillation (AMO):

“The Barents Sea has experienced consistently low extents, particularly in winter, and this year has been no different. While the Barents and Kara seas normally have close to 2 million square kilometers (772,000 square miles) of ice in February, recent years have seen 500,000 square kilometers (193,000 square miles) of ice extent or lower. This year, the Kara Sea is near average, but the Barents Sea remains low (Figure 4a). Unlike other regions in the Arctic, longer records of Barents Sea ice extent exist from records of fishing, whaling, and other activities. A recent paper (Miles et al., 2013 [2014, now in print]) examined these records, along with paleoproxy data, to examine extent over the past four hundred years. They found a 60- to 90-year cycle in Barents and Greenland seas ice extent related to the Atlantic Multidecadal Oscillation (AMO); the AMO is a basin-wide cycle of sea surface temperature variability similar to the El Niño and La Niña cycles in the Pacific, but varying over much longer periods. This research shows that in addition to the warming trend in the Arctic, some sea ice regions are likely also responding to natural climate variability.” [my bold]

The paper they cite (Miles et al. 2014, discussed elsewhere in December 2013 here) described the AMO this way:

“The AMO is a coherent pattern of basin-wide sea surface temperature (SST) variations with a period of roughly 60–90 years. ..Paleoenvironmental studies suggest that the AMO has persisted through previous centuries [Gray et al., 2004] and even millennia [Knudsen et al., 2011].”

Note that Miles and colleagues were looking at ice records on or around the sea ice maximum in winter/spring.

The Polar Bear Twist: Norwegian biologists Jon Aars and Magnus Andersen, who I’ve discussed before, have pointed out that the condition of polar bear males and females around Svalbard (Fig. 2) they examined over the last 20 years varied with the AMO and sea ice levels in spring and early summer. [research results posted at the website forEnvironmental Monitoring of Svalbard and Jan Mayen(MOSJ), Norwegian Polar Institute].

That makes a lot of sense to me, given that spring/early summer is the most critical feeding season for polar bears because it’s when fat young seals are most easily available.

It also makes sense to me that you may need a record hundreds of years long to understand the natural variability of Arctic Sea ice in its various regions. Recall that natural variation, not global warming, is now being used to explain the large variation in annual sea ice cover in the Bering Sea (home to Chukchi Sea polar bears). Continue reading

Posted onJune 21, 2013|Comments Off on Sea ice, beluga whales, and polar bear densities in the Gulf of Boothia

As I discussed in my last post, the Gulf of Boothia subpopulation in the central Canadian Arctic has the highest density of polar bears anywhere in the world. The question is, why?

For example, is the sea ice in the Gulf of Boothia region so markedly different from its nearest subpopulation-neighbor, M’Clintock Channel (Fig. 1), that it accounts for the wide disparity in polar bear densities between the two? The differences, remember, are dramatic: Gulf of Boothia, 18.3 bears per 1000 km2vs. M’Clintock Channel, 1.9. And while M’Clintock Channel may be low in part due to recent over-harvests (see footnote 1), even the density before over-harvests occurred in M’Clintock Channel were only 4.7, compared to 10.4 bears per 1000 km2 in Gulf of Boothia (see Table 1 in previous post).

Today, I’ll take a look at sea ice and ringed seal habitat in the Gulf of Boothia and M’Clintock Channel, as well as information from a study on polar bear diets, which together shine some light on why the Gulf of Boothia is such a great place for polar bears.

Figure 1. Map showing the side-by-side relationship of M’Clintock Channel and the Gulf of Boothia. From Barber and Iacozza (2004: Fig. 1).